Sulfonamide-containing indole compounds are useful as antitumor agents with angiogenesis inhibitory action, and among them, an especially notable antitumor effect is exhibited by N-(3-cyano-4-methyl-1H-indol-7-yl)-3-cyanobenzenesulfonamide (hereinafter referred to as “compound (5b)”) (see Patent document 1). A process for preparing the compound (5b) is disclosed in Example 1 of Patent document 1.
[Patent document 1] WO00/50395